From Tarzan & The Super 7:
Manta & Moray discover a pair of dolphins are breaking some whales and other sea creatures from captivity, unaware that those creatures are being studied and cared for by the humans.
Here's "The Freedom Fighters":
Joan Van Ark (Moray) would pick up a live-action gig soon after (Knots Landing), and since only 7 episodes were recorded, moved her cartoon gig to DePatie Freleng for the short-lived Spider-Woman the next season. Joe Stern (Manta) may not have had any other voice jobs after this was cancelled.
Also, some of the swimming scenes, either in tandem or Manta alone, look like they were redrawn from---who else?---Aquaman.